London: map of z value
Deciles of z value:
(-5.564, -1.023)
(-1.023, 0.174)
(0.174, 1.402)
(1.402, 2.584)
(2.584, 3.682)
(3.682, 4.973)
(4.973, 6.36)
(6.36, 8.478)
(8.478, 12.293)
(12.293, 43.01)